That's possible if you want to emphasise that defined end.
To my mind, you can use -taH anywhere that you can use -lI' (and -pu' anywhere that you can use -ta'), if you don't want to focus on the progress towards an end, even if there is progress being made. In other words, I don't think that -lI' and -ta' are mandatory even if there is a defined end.
They will often be accepted as alternative translations here, though, when it makes sense.
English uses "now" very broadly and can refer to the near future or the recent past. Klingon seems to use it more specifically to mean "at this moment in time". It may also include the near future and/or the recent past, but seems to always include this very moment, so is not appropriate for something that you are not doing now, but will be doing in the near future.